Big dream of mine would be to align nuclei of nuclear fuel atoms just so and then induce fission in such a way as to get one delayed neutron precursor and one other quick-to-stability fission product. This would allow fission power without any long-lived waste products or afterglow heat cooling challenges that dominate accident risk. Physicist friends have told me it's impossible. I've only accepted impractical for now.
You're thinking about the atom very classically, At the scale of the nucleus things just don't "exist" in "places". Processes are truly random and things literally don't have position/momentum/rotation/alignment until you do the thing that requires them to decide where they were and what they were doing at the time.
Simpler than nuclear physics is just the electron. There is no meaningful answer to where it is around an atom at any particular time. You can either get a location or a momentum or half the information about each if you poke it, but that's just its response to being poked, it wasn't "actually" there until you poked it.
Eh, not really. You can futz with the probability distribution, like a fast neutron will cause a different distribution of fission products than a slow one... but it is still a very random process. You can't control it like an expert at a billiards table. Especially the strong force mediated interactions between particles in the nucleus. Some people just won't believe you though.
More seriously, spin polarized D-T fusion is known to have an enhanced reaction cross section, so there are labs out there researching how to implement it more reliably.
that’s pretty much how windows update works (or used to work) to attempt to hot patch certain things without a reboot. Compiled functions in windows DLLs have a 5 byte prologue of nop instructions which is just long enough to overwrite with a jmp instruction to hook the function call and redirect it. https://devblogs.microsoft.com/oldnewthing/20110921-00/?p=95... In WinXP they started compiling this nop prologue in on purpose due to how useful it was. Before that, reverse engineers would need to get a bit lucky and find “room” for a jmp in some code path that was guaranteed to hit, in order to patch an executable without crashing it (iirc, i’m fuzzy on the details). Anyway, certainly not impossible, and we’d al be surprised by what can be made practical if the need is great enough.
For MRI / medical imaging, if nuclear wobbling can enhance signal strength, it might be possible to achieve high-quality images using lower-strength magnetic fields, and much faster. Maybe even ones that fit in a backpack and unfold.
For comparison, it seems the smallest portable MRI presently are ~600kg, like the Hyperfine Swoop https://hyperfine.io/swoop/overview (not affiliated).
I’m not totally sure what makes this result so novel but also that’s probably due to my ignorance. Hyperfine qubits are pretty common using neutral atoms, and you can do imaging on the hyperfine states. Is the novelty here that the electron spin is on resonance with the nuclear spin and that it’s done with STM? I guess I don’t see how pump-probe is so much more direct than using an imaging transition.
I think the key thing they were pointing out was the ability to store information inside a nucleus that can be read back (reminds me of how core memory worked on the old Apollo 11 Era computers) which could be a very reliable and dense memory. It's reliable because the electron shell is sort of protecting the information stored inside the nucleus.
I wonder if they'll have the same issue that core memory also had which is that by reading the magnetic state you also destroy that state, and so every bit 'read' operation has to be followed with a 'now write the bit back again' step.
Entanglement isn't particularly useful for communication, you can't send bits without sending photons (or similar) physically. Quantum mechanics doesn't permit ansibles as far as anyone knows.
While the second and third parts if your comment are complete true, the first part
> Entanglement isn't particularly useful for communication
I would say is false. Entanglement lets you do some fun and theoretically useful stuff for communication tasks. At the most basic level sharing entanglement lets you upgrade a classical communication channels you have into a quantum one (sending 2 bits and burning an entangled pair lets you send a qubit). You can do increasing fancy stuff if you so wish, if you are sufficiently paranoid you might be interested in device independent cryptography, which is only possible because of entanglement.
Isn't it true that in key exchange entanglement isn't used in any way shape or form for sending data, but only in making a determination that there was no eavesdropping on the transmission, because any eavesdropper would collapse the wave function.
So like you said, entanglement can't be used to send information, but it can be used to detect if the transmission was secure (I think)
There are many protocols for quantum key distribution/exchange so it's hard to answer fully without knowing which one you're talking about. That said their are protocols, like the one invented by Artur Ekert in 1991, which use entanglement in an essential way to transmit the key. Even in the absence of an evesdropper the protocol will not work without entanglement. It escapes the no-communication theorem by also requiring some classical communication.
Right, if you expand the scope of the discussion to other areas other than sending bits, there are various ways entanglement is used in various protocols. But none of them utilize entanglement to be able to get a bit from Alice to Bob faster than light can go.
Is it the issue or is it rather than any measurement of entangled quantum state change is modifying the measurement to the extent that there is a chicken and egg problem?
Basically reading quantum data is also a write operation?
Thanks. The reason still seem to be related to the uncertainty principle although I am not sure.
The same way they explain no-cloning but it seems to be analogous to identity within a system with interaction from neighboring data.
Ultimately there is no pure independent state. Data always exists within context. Hence causality and spatial preservation (no instant physical teleportation as far as is currently understood). (in very layman's terms)
I am unable to grasp why FTL communication would break causality, it's like my brain just refuses to accept it. Seriously, I've had it explained several times over the years.
Its probably mostly because you have an intuitive idea that there is some concept of "now" which is independent of the observer.
In special relativity this global "now" isn't a thing. It doesn't exist. There is no global now. Different observers who are in different places and/or moving at different speeds will describe different events as simultaneous.
In particular say we have an observer who sees an event A happening at time 0, and a second event (call it B) at time t and the distance between them is greater than c t. Then you can find observers who see A happening first, B happening first or the two happening at the same time. However all observers will agree that the distance between the events was greater than c times the time between them.
This seems like it would cause problems with causality, but it doesn't because we need the distance to be greater than c times the time, which means no lightspeed signal could get from A to B. If you allow ftl communication then this "escape" doesn't work anymore, and causality can be explicitly broken.
When you communicate, you're sending energy - whether it's sound waves or radio waves or whatever. Energy can't travel faster than c through spacetime. Now if you manipulate spacetime, such as a wormhole or whatever, then the end result can effectively appear as if it's FTL but its still going at c, its just traveling through less/compressed space.
There was a young lady named Bright,
Whose speed was much faster than light.
She went out one day
In a relative way
And returned on the previous night.
Time flows differently depending on velocity with respect to your frame of reference. Two observers moving at different speeds with respect to each other see different time flows. At normal speeds this is negligible but at close to light speed... hoo boy. You get things like observers seeing events occur separately that occured simultaneously for their counterparts and so forth. So if you were able to send information faster than light somehow, you would be sending it from one frame of reference with one notion of time into another frame of reference with a different notion of time -- one which observes receipt of the message before it can observe the sender sending it!
It's all a big ball of wibbly-wobbly, timey-wimey stuff.
If you have two very very long trains several light years long, passing each other in opposite directions, and each train has FTL-comm devices, and the front and back end of each train can flash signal lamps that are synchronized with each other, your train will see the other train's rear lamp flash long before the other train's front lamp. The other train's front FTL-comm is sending messages 'back in time' to reach the other train's rear FTL-comm. By sending signals from your front, to your rear, to their front, to their rear, and back to your front, the message arrives before you sent it. So we think FTL-comm can not work.
One intuitive explanation is that anything moving at the speed of light is experiencing no time at all (from the point of view of an observer) and if something is moving faster than light that means it's going backwards in time. (only massless virtual particles can)
If a clock stops or runs backwards that totally messes up "causality" which is about events interacting relative to a time order, and so time must exist for causality to make sense.
If you did manage FTL communication, it seems like it might let you detect the notional absolute rest frame, so you'd be breaking special relativity anyway.
Yeah that's the point of the article really. The rest of special relativity remains intact though for subluminal particles, you still have Lorentz transforms and energy-mass equivalence and all that stuff.
You can't grasp this because there is no FTL communication. Quantum entanglement does not enable FTL communication, and wormholes etc. are entirely theoretical.
It doesn't even enable STL communication, other than eg superdense coding and similar. But that's not what people mean when they think entanglement can be used for communication.
Big dream of mine would be to align nuclei of nuclear fuel atoms just so and then induce fission in such a way as to get one delayed neutron precursor and one other quick-to-stability fission product. This would allow fission power without any long-lived waste products or afterglow heat cooling challenges that dominate accident risk. Physicist friends have told me it's impossible. I've only accepted impractical for now.
You're thinking about the atom very classically, At the scale of the nucleus things just don't "exist" in "places". Processes are truly random and things literally don't have position/momentum/rotation/alignment until you do the thing that requires them to decide where they were and what they were doing at the time.
Simpler than nuclear physics is just the electron. There is no meaningful answer to where it is around an atom at any particular time. You can either get a location or a momentum or half the information about each if you poke it, but that's just its response to being poked, it wasn't "actually" there until you poked it.
> Processes are truly random
You can get a Nobel prize or two by proving this.
We don't know about random yet, just that there's no hidden variable.
Some say that it has not been fully proved there are no hidden variables.
https://youtu.be/ytyjgIyegDI?t=86 (Sabine Hossenfelder on Superdeterminism)
From what I recall, quantum things have well defined states, even if those states may not correspond to position / momentum / rotation / alignment.
By correctly molding the energy landscape it may be possible to set the states and state transitions up in a beneficial way for what he proposed.
Eh, not really. You can futz with the probability distribution, like a fast neutron will cause a different distribution of fission products than a slow one... but it is still a very random process. You can't control it like an expert at a billiards table. Especially the strong force mediated interactions between particles in the nucleus. Some people just won't believe you though.
I'm a big believer in Energy Wave Theory.
The universe... just one big wave function perhaps
https://en.m.wikipedia.org/wiki/Wheeler%E2%80%93DeWitt_equat...
You want an msr/LFTR and breed away the bad waste.
Now that’s what I’d call nuclear engineering!
More seriously, spin polarized D-T fusion is known to have an enhanced reaction cross section, so there are labs out there researching how to implement it more reliably.
In software terms, this would be as difficult as switching out specific bits from a running program to fix bugs.
Certainly not impossible, but impractical as far as we can see.
that’s pretty much how windows update works (or used to work) to attempt to hot patch certain things without a reboot. Compiled functions in windows DLLs have a 5 byte prologue of nop instructions which is just long enough to overwrite with a jmp instruction to hook the function call and redirect it. https://devblogs.microsoft.com/oldnewthing/20110921-00/?p=95... In WinXP they started compiling this nop prologue in on purpose due to how useful it was. Before that, reverse engineers would need to get a bit lucky and find “room” for a jmp in some code path that was guaranteed to hit, in order to patch an executable without crashing it (iirc, i’m fuzzy on the details). Anyway, certainly not impossible, and we’d al be surprised by what can be made practical if the need is great enough.
> 5 byte prologue of nop instructions
Has this been around long enough that CPUs optimise it out?
I presume there is a long list of CPU optimisations that are specific to the quirks of Windows object code . . .
For MRI / medical imaging, if nuclear wobbling can enhance signal strength, it might be possible to achieve high-quality images using lower-strength magnetic fields, and much faster. Maybe even ones that fit in a backpack and unfold.
For comparison, it seems the smallest portable MRI presently are ~600kg, like the Hyperfine Swoop https://hyperfine.io/swoop/overview (not affiliated).
I’m not totally sure what makes this result so novel but also that’s probably due to my ignorance. Hyperfine qubits are pretty common using neutral atoms, and you can do imaging on the hyperfine states. Is the novelty here that the electron spin is on resonance with the nuclear spin and that it’s done with STM? I guess I don’t see how pump-probe is so much more direct than using an imaging transition.
I think the key thing they were pointing out was the ability to store information inside a nucleus that can be read back (reminds me of how core memory worked on the old Apollo 11 Era computers) which could be a very reliable and dense memory. It's reliable because the electron shell is sort of protecting the information stored inside the nucleus.
I wonder if they'll have the same issue that core memory also had which is that by reading the magnetic state you also destroy that state, and so every bit 'read' operation has to be followed with a 'now write the bit back again' step.
[flagged]
CTRL+F "entanglement". Disappointed.
No interstellar comms for us.
Entanglement isn't particularly useful for communication, you can't send bits without sending photons (or similar) physically. Quantum mechanics doesn't permit ansibles as far as anyone knows.
While the second and third parts if your comment are complete true, the first part
> Entanglement isn't particularly useful for communication
I would say is false. Entanglement lets you do some fun and theoretically useful stuff for communication tasks. At the most basic level sharing entanglement lets you upgrade a classical communication channels you have into a quantum one (sending 2 bits and burning an entangled pair lets you send a qubit). You can do increasing fancy stuff if you so wish, if you are sufficiently paranoid you might be interested in device independent cryptography, which is only possible because of entanglement.
Yes, they are fun, but not notably useful, at least not yet. And only useful for pretty specialized tasks like key exchange.
Isn't it true that in key exchange entanglement isn't used in any way shape or form for sending data, but only in making a determination that there was no eavesdropping on the transmission, because any eavesdropper would collapse the wave function.
So like you said, entanglement can't be used to send information, but it can be used to detect if the transmission was secure (I think)
There are many protocols for quantum key distribution/exchange so it's hard to answer fully without knowing which one you're talking about. That said their are protocols, like the one invented by Artur Ekert in 1991, which use entanglement in an essential way to transmit the key. Even in the absence of an evesdropper the protocol will not work without entanglement. It escapes the no-communication theorem by also requiring some classical communication.
Right, if you expand the scope of the discussion to other areas other than sending bits, there are various ways entanglement is used in various protocols. But none of them utilize entanglement to be able to get a bit from Alice to Bob faster than light can go.
I had to google ansible. https://en.wikipedia.org/wiki/Ansible
Is it the issue or is it rather than any measurement of entangled quantum state change is modifying the measurement to the extent that there is a chicken and egg problem?
Basically reading quantum data is also a write operation?
The issue the person above is alluding to is known as the no communication theorem.
It has a wiki page
https://en.m.wikipedia.org/wiki/No-communication_theorem
But the upshot is basically that entanglement doesn't let you do anything unless you send some classical data as well.
Thanks. The reason still seem to be related to the uncertainty principle although I am not sure.
The same way they explain no-cloning but it seems to be analogous to identity within a system with interaction from neighboring data. Ultimately there is no pure independent state. Data always exists within context. Hence causality and spatial preservation (no instant physical teleportation as far as is currently understood). (in very layman's terms)
I am unable to grasp why FTL communication would break causality, it's like my brain just refuses to accept it. Seriously, I've had it explained several times over the years.
Its probably mostly because you have an intuitive idea that there is some concept of "now" which is independent of the observer.
In special relativity this global "now" isn't a thing. It doesn't exist. There is no global now. Different observers who are in different places and/or moving at different speeds will describe different events as simultaneous.
In particular say we have an observer who sees an event A happening at time 0, and a second event (call it B) at time t and the distance between them is greater than c t. Then you can find observers who see A happening first, B happening first or the two happening at the same time. However all observers will agree that the distance between the events was greater than c times the time between them.
This seems like it would cause problems with causality, but it doesn't because we need the distance to be greater than c times the time, which means no lightspeed signal could get from A to B. If you allow ftl communication then this "escape" doesn't work anymore, and causality can be explicitly broken.
When you communicate, you're sending energy - whether it's sound waves or radio waves or whatever. Energy can't travel faster than c through spacetime. Now if you manipulate spacetime, such as a wormhole or whatever, then the end result can effectively appear as if it's FTL but its still going at c, its just traveling through less/compressed space.
It's all a big ball of wibbly-wobbly, timey-wimey stuff.
If you have two very very long trains several light years long, passing each other in opposite directions, and each train has FTL-comm devices, and the front and back end of each train can flash signal lamps that are synchronized with each other, your train will see the other train's rear lamp flash long before the other train's front lamp. The other train's front FTL-comm is sending messages 'back in time' to reach the other train's rear FTL-comm. By sending signals from your front, to your rear, to their front, to their rear, and back to your front, the message arrives before you sent it. So we think FTL-comm can not work.
One intuitive explanation is that anything moving at the speed of light is experiencing no time at all (from the point of view of an observer) and if something is moving faster than light that means it's going backwards in time. (only massless virtual particles can)
If a clock stops or runs backwards that totally messes up "causality" which is about events interacting relative to a time order, and so time must exist for causality to make sense.
https://forwardscattering.org/post/36
If you did manage FTL communication, it seems like it might let you detect the notional absolute rest frame, so you'd be breaking special relativity anyway.
Yeah that's the point of the article really. The rest of special relativity remains intact though for subluminal particles, you still have Lorentz transforms and energy-mass equivalence and all that stuff.
That post is very straightforward, thank you!
You can't grasp this because there is no FTL communication. Quantum entanglement does not enable FTL communication, and wormholes etc. are entirely theoretical.
It doesn't even enable STL communication, other than eg superdense coding and similar. But that's not what people mean when they think entanglement can be used for communication.